@article{vasquez_dvorak_1996, title={Trends in variances and heritabilities with stand development of tropical pines}, volume={26}, ISSN={["1208-6037"]}, DOI={10.1139/x26-164}, abstractNote={ Phenotypic and additive genetic variances as well as narrow-sense heritability for cumulative height were determined from assessments of tropical pine (Pinuscaribaea Morelet, Pinuschiapensis (Mart.) Andresen, and Pinustecunumanii (Schw.) Eguiluz et Perry) trials established in South America and South Africa by the Central America and Mexico Coniferous Resources (CAMCORE) Cooperative. Cumulative stem height was analyzed from 1-, 3-, 5-, and 8-year data collected on open-pollinated families to determine additive genetic and phenotypic variances. Variances based on arithmetic as well as log-transformed values are presented. Phenotypic and genetic variances of log-transformed values decreased over time, probably reflecting the onset of intergenotypic competition. Absolute variances increased over time as the trials became older, but the rate of increase for phenotypic variance was greater than that for additive variance. Individual narrow-sense heritabiiities changed over time but without showing any definite trend by species. It appeared that variance trends reflected the varying ontogenetic changes during the development of the stands, which could be indicated by size of the trees rather than by their age. Breeding strategies in tropical pines should consider the increasing intensity of environmental effects as a stand matures, since they cause a decline of genetic variances at a higher rate than phenotypic variances. Furthermore, it is hypothesized that a phenotypic trait at a given ontogenetic stage of the individual is under temporal control of a set of genes that changes as the temporal environmental conditions change. }, number={8}, journal={CANADIAN JOURNAL OF FOREST RESEARCH}, author={Vasquez, J and Dvorak, WS}, year={1996}, month={Aug}, pages={1473–1480} }